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The paper presents research on a system for measuring the parameters of a vehicle in motion and the process of validating it under laboratory conditions. The measurement system uses four inductive-loop (IL) sensors, two slim ILs and two wide ILs. The vehicle speed, wheelbase, length, and overhangs are all determined on the basis of a vehicle magnetic profile (VMP) waveform. VMPs are captured from the continuous IL-based impedance measurement. The impedance measurement for a single IL is performed simultaneously at three carrier frequencies. The uncontrolled measurement conditions in the field on a real road test bed (RTB), including the speed of passing vehicles, motivated the development of a laboratory test bed (LTB). This LTB serves as a model of an existing measurement setup installed on the road, i.e., the RTB. The LTB includes IL sensors and a movable model of the vehicle made in 1:50 scale. The LTB enables validation of the whole measurement system in the vehicle speed range from 10 km/h up to 150 km/h in 5 km/h increments in fully controlled conditions. The measurement results are presented in the distance domain, calculated from the VMPs and the measured speed. The largest errors in estimating vehicle-model body parameters, on a natural scale, do not exceed 4.3 cm.

Additive manufacturing (AM) offers exciting opportunities to manufacture parts of unprecedented complexity. Topology optimization is essential to fully exploit this capability. However, AM processes have specific limitations as well. When these are not considered during design optimization, modifications are generally needed in post-processing, which add costs and reduce the optimized performance. This paper presents a filter that incorporates the main characteristics of a generic AM process, and that can easily be included in conventional density-based topology optimization procedures. Use of this filter ensures that optimized designs comply with typical geometrical AM restrictions. Its performance is illustrated on compliance minimization problems, and a 2D Matlab implementation is provided.

In order to improve the ability of selective laser melting (SLM) to form unsupported overhang structures of titanium alloys, this paper carried out a study on the dimensional accuracy and surface quality of the overhang structures. In this study, the mechanism of the effect of different factor interactions on the accuracy of the overhang structure was evaluated by analysis of variance. The influence mechanism of SLM process parameters on the surface quality of the fabricated parts was investigated. The experiment results indicate that laser power, scanning speed, and powder thickness have a significant impact on the dimensional accuracy of overhang structures fabricated by SLM. The inability to replenish the powder in the overhang area and the differences in cooling rates of the melt pool at different locations are the main reasons causing the phenomena of the overhang angle of less than 90° and the lower convex of the overhanging undersurface. Increasing the designed overhang thickness (at least 3 mm) can effectively enhance the quality of the overhang upper surface. When the laser energy density was 75-85 J/mm 3 , the overhang upper surface obtained a better surface quality. The difference in surface roughness between the overhanging side surface and the non-overhanging side surface can be improved by using process parameters with a laser energy density in the range of 90-100 J/mm 3 . The optimal process parameters for forming unsupported overhang structures were determined in the experiment to be a laser power of 200 W, a scanning speed of 800 mm/s, and a powder thickness of 30 μm.

Previous empirical studies find that lottery-like stocks significantly underperform their non-lottery-like counterparts. Using five different measures of the lottery features in the literature, we document that the anomalies associated with these measures are state dependent: the evidence supporting these anomalies is strong and robust among stocks where investors have lost money, whereas among stocks where investors have gained profits, the evidence is either weak or even reversed. Several potential explanations for such empirical findings are examined, and we document support for the explanation based on reference-dependent preferences. Our results provide a unified framework to understand the lottery-related anomalies in the literature. This paper was accepted by Tyler Shumway, finance.

Additive manufacturing (AM) enables the fabrication of parts of unprecedented complexity. Dedicated topology optimization approaches, that account for specific AM restrictions, are instrumental in fully exploiting this capability. In popular powder-bed-based AM processes, the critical overhang angle of downward facing surfaces limits printability of parts. This can be addressed by changing build orientation, part adaptation, or addition of sacrificial support structures. Thus far, each of these measures have been studied separately and applied sequentially, which leads to suboptimal solutions or excessive computation cost. This paper presents and studies, based on 2D test problems, an approach enabling simultaneous optimization of part geometry, support layout and build orientation. This allows designers to find a rational tradeoff between manufacturing cost and part performance. The relative computational cost of the approach is modest, and in numerical tests it consistently obtains high quality solutions.

Self-discharge of lithium-ion cells leads to voltage decay over time. In this work, the self-discharge was measured at 30 ∘C for three cell types at various voltage levels for about 150 days in a constant voltage mode determining the current at a high precision (float current). All cells exhibit a transient part leading to a steady-state, which is no longer influenced by reversible effects. To study the effect of the check-ups on the steady-state float current, the cells, interrupted and not interrupted by check-ups, were compared. The results indicate that both the transient processes and steady-state currents are highly reproducible. In the first period of the float current, the polarization dominates the measured current, followed by the anode overhang effect dominating the process for a period of 5–30 days. After the decline of both processes, a mostly constant steady-state in the order of μA is observed. The check-up interruption generally shows no apparent effect on the reached steady-state and results only in an extended settling time. A model to simulate the transient process and steady-state of float currents was developed. The model shows a high accuracy in reproducing the results and identifying the time needed to reach the steady-state.

This work falls within the scope of computer-aided optimal design, and aims to integrate the topology optimization procedures and recent additive manufacturing technologies (AM). The elimination of scaffold supports at the topology optimization stage has been recognized and pursued by many authors recently. The present paper focuses on implementing a novel and specific overhang constraint that is introduced inside the topology optimization problem formulation along with the regular volume constraint. The proposed procedure joins the design and manufacturing processes into a integrated workflow where any component can directly be manufactured with no requirement of any sacrificial support material right after the topology optimization process. The overhang constraint presented in this work is defined by the maximum allowable inclination angle, where the inclination of any member is computed by the Smallest Univalue Segment Assimilating Nucleus (SUSAN), an edge detection algorithm developed in the field of image analysis and processing. Numerical results on some benchmark examples, along with the numerical performances of the proposed method, are introduced to demonstrate the capacities of the presented approach.

This paper studies additive manufacturing (AM) oriented structural topology optimization (TO). The minimum compliance design subject to overhang angle constraint with overhang length relaxation and horizontal minimum length control is considered. Although the overhang length relaxation allows additional flexibility for AM product design, there have been very limited studies on it. This paper elucidates that the overhang angle constraint we proposed can identify the lower boundary element that violates the overhang angle constraint. Taking advantage of this fact, we achieve the overhang length relaxation by specifying that the volume fraction of the elements that violate the overhang angle constraint in each local area of the design domain is less than a specified upper bound. A formula for estimating the maximum allowable overhang length of this method is proposed and verified. The horizontal minimum length constraint is also employed in this paper. While controlling the horizontal length size of the structural member, this constraint together with the overhang angle constraint with overhang length relaxation suppresses the hanging feature. The gradient-based optimization algorithm method of moving asymptotic (MMA) is used to solve the TO formulation. Numerical examples show the effectiveness of this method. It is observed that the new constraint alleviates the main issues of traditional overhang angle constraints, i.e., gray element issue, stress concentration issue, and shattered structure issue. Compared with the strict traditional overhang angle constraint, the new formulation reduces structural compliance.

Additive manufacturing enables the nearly uncompromised production of optimized topologies. However, due to the overhang limitation, some designs require a large number of supporting structures to enable manufacturing. Because these supports are costly to build and difficult to remove, it is desirable to find alternative designs that do not require support. In this work, a filter is presented that suppresses non-manufacturable regions within the topology optimization loop, resulting in designs that can be manufactured without the need for supports. The filter is based on front propagation, can be evaluated efficiently, and adjoint sensitivities are calculated with almost no additional computational cost. The filter can be applied also to unstructured meshes and the permissible degree of overhang can be freely chosen. The method is demonstrated on several compliance minimization problems in which its computational efficiency and flexibility are shown. The current applications are in 2D, and the proposed method is readily extensible to 3D.

This article falls within the scope of topology optimization for Additive Manufacturing processes and proposes an alternative strategy to prevent the phenomenon known as the Dripping Effect. The Dripping Effect is when an overhang constraint is imposed on topology optimization processes for Additive Manufacturing and is defined as the formation of oscillatory contour trends within the prescribed threshold angle. Although these drop-like formations constitute local minimizers of the constraint function, they do not provide a printable feature, and, therefore, they neither eliminate the need to form temporary support structures. So far, there has been no general agreement on how to prevent the Dripping Effect, so this work aims to introduce a strategy that effectively prevents it, and that at the same time may be easy to extrapolate to other types of geometric overhang restrictions. This paper provides a study of the origin of the Dripping Effect and gives detailed instructions on how the proposed prevention strategy is applied. In addition, several benchmark examples where the Dripping Effect is prevented are shown.